The role of champions in the implementation of technology in healthcare services: a systematic mixed studies review

Background Champions play a critical role in implementing technology within healthcare services. While prior studies have explored the presence and characteristics of champions, this review delves into the experiences of healthcare personnel holding champion roles, as well as the experiences of healthcare personnel interacting with them. By synthesizing existing knowledge, this review aims to inform decisions regarding the inclusion of champions as a strategy in technology implementation and guide healthcare personnel in these roles. Methods A systematic mixed studies review, covering qualitative, quantitative, or mixed designs, was conducted from September 2022 to March 2023. The search spanned Medline, Embase, CINAHL, and Scopus, focusing on studies published from 2012 onwards. The review centered on health personnel serving as champions in technology implementation within healthcare services. Quality assessments utilized the Mixed Methods Appraisal Tool (MMAT). Results From 1629 screened studies, 23 were included. The champion role was often examined within the broader context of technology implementation. Limited studies explicitly explored experiences related to the champion role from both champions’ and health personnel’s perspectives. Champions emerged as promoters of technology, supporting its adoption. Success factors included anchoring and selection processes, champions’ expertise, and effective role performance. Discussion The specific tasks and responsibilities assigned to champions differed across reviewed studies, highlighting that the role of champion is a broad one, dependent on the technology being implemented and the site implementing it. Findings indicated a correlation between champion experiences and organizational characteristics. The role’s firm anchoring within the organization is crucial. Limited evidence suggests that volunteering, hiring newly graduated health personnel, and having multiple champions can facilitate technology implementation. Existing studies predominantly focused on client health records and hospitals, emphasizing the need for broader research across healthcare services. Conclusions With a clear mandate, dedicated time, and proper training, health personnel in champion roles can significantly contribute professional, technological, and personal competencies to facilitate technology adoption within healthcare services. The review finds that the concept of champions is a broad one and finds varied definitions of the champion role concept. This underscores the importance of describing organizational characteristics, and highlights areas for future research to enhance technology implementation strategies in different healthcare settings with support of a champion. Supplementary Information The online version contains supplementary material available at 10.1186/s12913-024-10867-7.

The role of champions in the implementation of technology in healthcare services: a systematic mixed studies review Sissel Pettersen 1* , Hilde Eide 2 and Anita Berg 1

Background
Digital health technologies play a transformative role in healthcare service systems [1,2].The utilization of technology and digitalization is essential for ensuring patient safety, delivering high quality, cost-effective, and sustainable healthcare services [3,4].The implementation of technology in healthcare services is a complex process that demands systematic changes in roles, workflows, and service provision [5,6].
The successful implementation of new technologies in healthcare services relies on the adaptability of health professionals [7,8,9].Champions have been identified as a key factor in the successful implementation of technology among health personnel [10][11][12].However, they have rarely been studied as an independent strategy; instead, they are often part of a broader array of strategies in implementation studies (e.g., Hudson [13], Gullslett and Bergmo [14]).Prior research has frequently focused on determining the presence or absence of champions [10,12,15], as well as investigating the characteristics of individuals assuming the champion role (e.g., George et al. [16], Shea and Belden [17]).
Recent reviews on champions [18,19,20] have studied their effects on adherence to guidelines, implementation of innovations and facilitation of evidence-based practice.While these reviews suggest that having champions yields positive effects, they underscore the importance for studies that offer detailed insights into the champion's role concerning specific types of interventions.
There is limited understanding of the practical role requirements and the actual experiences of health personnel in performing the champion role in the context of technology implementation within healthcare services.Further, this knowledge is needed to guide future research on the practical, professional, and relational prerequisites for health personnel in this role and for organizations to successfully employ champions as a strategy in technology implementation processes.
This review seeks to synthesize the existing empirical knowledge concerning the experiences of those in the champion role and the perspectives of health personnel involved in technology implementation processes.The aim is to contribute valuable insights that enhance our understanding of practical role requirements, the execution of the champion role, and best practices in this domain.
The term of champions varies [10,19] and there is a lack of explicit conceptualization of the term 'champion' in the implementation literature [12,18].Various terms for individuals with similar roles also exist in the literature, such as implementation leader, opinion leader, facilitator, change agent, superuser and facilitator.For the purpose of this study, we have adopted the terminology utilized in the recent review by Rigby, Redley and Hutchinson [21] collectively referring to these roles as 'champions' .This review aims to explore the experiences of health personnel in their role as champions and the experiences of health personnel interacting with them in the implementation of technology in the healthcare services.

Methods
Prior review studies on champions in healthcare services have employed various designs [10,18,19,20].In this review, we utilized a comprehensive mixed studies search to identify relevant empirical studies [22].The search was conducted utilizing the Preferred Reporting Items for Systematic and Meta-Analysis (PRISMA) guidelines, ensuring a transparent and comprehensive overview that can be replicated or updated by others [23].The study protocol is registered in PROSPERO (ID CRD42022335750), providing a more comprehensive description of the methods [24].A systematic mixed studies review, examining research using diverse study designs, is well-suited for synthesizing existing knowledge and identifying gaps by harnessing the strengths of both qualitative and quantitative methods [22].Our search encompassed qualitative, quantitative, and mixed methods design to capture experiences with the role of champions in technology implementation.

Search strategy
The first author, in collaboration with a librarian, developed the search strategy based on initial searches to identify appropriate terms and truncations that align with the eligibility criteria.The search was constructed utilizing a combination of MeSH terms and keywords related to technology, implementation, champion, and attitudes/ experiences.Conducted in August/September 2022, the search encompassed four databases: Medline, Embase, CINAHL, and Scopus, with an updated search conducted in March 2023.The full search strategy for Medline is provided in Appendix 1.The searches in Embase, CINAHL and Scopus employed the same strategy, with adopted terms and phrases to meet the requirements of each respective database.

Eligibility criteria Inclusion
We included all empirical studies employing qualitative, quantitative, and mixed methods designs that detailed the experiences and/or attitudes of health personnel regarding the champions role in the implementation of technology in healthcare services.Articles in the English language published between 2012 and 2023 were considered.The selected studies involved technology implemented or adapted within healthcare services.

Exclusion
Conference abstract and review articles were excluded from consideration.Articles published prior 2012 were excluded as a result of the rapid development of technology, which could impact the experiences reported.Furthermore, articles involving surgical technology and pre-implementation studies were also excluded, as the focus was on capturing experiences and attitudes from the adoption and daily use of technology.The study also excluded articles that involved champions without clinical health care positions.

Study selection
A total of 1629 studies were identified and downloaded from the selected databases, with Covidence [25] utilized as a software platform for screening.After removing 624 duplicate records, all team members collaborated to calibrate the screening process utilizing the eligibility criteria on the initial 50 studies.Subsequently, the remaining abstracts were independently screened by two researchers, blinded to each other, to ensure adherence to the eligibility criteria.Studies were included if the title and abstract included the term champion or its synonyms, along with technology in healthcare services, implementation, and health personnel's experiences or attitudes.Any discrepancies were resolved through consensus among all team members.A total of 949 abstracts were excluded for not meeting this inclusion condition.During the initial search, 56 remaining studies underwent full-text screening, resulting in identification of 22 studies qualified for review.
In the updated search covering the period September 2022 to March 2023, 64 new studies were identified.Of these, 18 studies underwent full-text screening, and one study was included in our review.The total number of included studies is 23.The PRISMA flowchart (Fig. 1) illustrates the process.

Data extraction
The research team developed an extraction form for the included studies utilizing an Excel spreadsheet.Following data extraction, the information included the Name of Author(s) Year of publication, Country/countries, Title of the article, Setting, Aim, Design, Participants, and Sample size of the studies, Technology utilized in healthcare services, name/title utilized to describe the Champion Role, how the studies were analyzed and details of Attitude/Experience with the role of champion.Data extraction was conducted by SP, and the results were deliberated in a workshop with the other researchers AB, and HE until a consensus was reached.Any discrepancies were resolved through discussions.The data extraction was categorized into three categories: qualitative, quantitative, and mixed methods, in preparation for quality appraisal.

Quality appraisal
The MMAT [26] was employed to assess the quality of the 23 included studies.Specifically designed for mixed studies reviews, the MMAT allows for the appraisal of the methodological quality of studies falling into five categories.The studies in our review encompassed qualitative, quantitative descriptive, and mixed methods studies.The MMAT begins with two screening questions to confirm the empirical nature of this study.Subsequently, all studies were categorized by type and evaluated utilizing specific criteria based on their research methods, with ratings of 'Yes, ' 'No' or 'Can't tell.' The MMAT discourages overall scores in favor of providing a detailed explanation for each criterion.Consequently, we did not rely on the MMAT's overall methodical quality scores and continued to include all 23 studies for our review.Two researchers independently scored the studies, and any discrepancies were discussed among all team members until a consensus was reached.The results of the MMAT assessments are provided in Appendix 2.

Data synthesis
Based on discussions of this material, additional tables were formulated to present a comprehensive overview of the study characteristics categorized by study design, study settings, technology included, and descriptions/ characteristics of the champion role.To capture attitudes and experiences associated with the champion role, the findings from the included studies were translated into narrative texts [22].Subsequently, the reviewers worked collaboratively to conduct a thematic analysis, drawing inspiration from Braun and Clarke [27].Throughout the synthesis process, multiple meetings were conducted to discern and define the emerging themes and subthemes.
The adopting of new technology in healthcare services can be perceived as both an event and a process.According to Iqbal [28], experience is defined as the knowledge and understanding gained after an event or the process of living through or undergoing an event.This review synthesizes existing empirical knowledge regarding the experiences of occupying the champion role, and the perspectives of health personnel interacting with champions in technology implementation processes.

Study characteristics
The review encompassed a total of 23 studies, and an overview of these studies is presented in Table 1.Of these, fourteen studies employed a qualitative design, four had quantitative design, and five utilized a mixed method design.The geographical distribution revealed that the majority of studies were conducted in the USA (8), followed by Australia (5), England (4), Canada (2),      Norway (2), Ireland (1), and Malaysia (1).In terms of settings, 11 studies were conducted in hospitals, five in primary health care, three in home-based care settings, and four in a mixed settings where two or more settings collaborated.Various technologies were employed across these studies, with client health records (7) and telemedicine (5) being the most frequently utilized.All studies included experiences from champions or health personnel collaborating with champions in their respective healthcare services.Only three studies had the champion role as a main objective [29,30,31].The remaining studies described champions as one of the strategies in technology implementation processes, including 10 evaluation studies (including feasibility studies [32,33,34] and one cost-benefit study [30]).

Sample
Several studies underscored the importance of champions for successful implementation [29-31, 34-38, 40-43, 49].Four studies specifically highlighted champions as a key factor for success [34,36,37,43], and one study went further to describe champions as the most important factor for successful implementation [39].Additionally, one study associated champions with reduced labor cost [30].

Thin descriptions, yet clear expectations for technology champions' role and -attributes
The analyses revealed that the concept of champions in studies pertaining to technology implementation in healthcare services varies, primarily as a result of the diversity of terms utilized to describe the role combined with short role descriptions.Nevertheless, the studies indicated clear expectations for the champion's role and associated attributes.
Most studies associated champion roles with specific professions.In seven studies, the professional title was explicitly linked to the concept of champions, such as physician champions or clinical nurse champions, or through the strategic selection of specific professions [29,33,36,40,43,47,50].Additionally, some studies did not specify professions, but utilized terms like clinicians [45] or health professionals [41].
Eight studies provided a specific description or definition of the champion [29-32, 38, 48-50].The champion's role was described as involving training in the specific technology, being an expert on the technology, providing support and assisting peers when needed.In some instance, the champion had a role in leading the implementation [50], while in other situations, the champion operated as a mediator [48].

Desirable champion attributes
To effectively fulfill their role, champions should ideally possess clinical expertise and experience [29,35,38,40,48], stay professionally updated [37,48], and possess knowledge of the organization and workflows [29,34,46].They should have the ability to understand and communicate effectively with healthcare personnel [31,32,46,49] and be proficient in IT language [51].Moreover, champions should demonstrate a general technological interest and competence, and competence, along with specific knowledge of the technology to be implemented [32,37,49].It is also emphasized that they should command formal and/or informal respect and authority in the organization [36,45], be accessible to others [39,43], possess leadership qualities [34,37,38,46], and understand and balance the needs of stakeholders [43].Lastly, the champions should be enthusiastic promoters of the technology, engaging and supporting others [31-34, 37, 39-41, 43, 49], while also effectively coping with cultural resistance to change [31,46].

Anchoring and recruiting for the champion role
The champions were organized differently within services, holding various positions in the organizations, and being recruited for the role in different ways.

Anchoring the champion role
The champion's role is primarily anchored at two levels: the management level and/or the clinical level, with two studies having champions at both levels [34,49].Those working with the management actively participated in the planning of the technology implementation [29,36,40,41,45].Serving as advisors to management, they leveraged their clinical knowledge to guide the implementation in alignment with the necessities and possibilities of daily work routines in the clinics.Champions in this capacity experienced having a clear formal position that enabled them to fulfil their role effectively [29,40].Moreover, these champions served as bridge builders between the management and department levels [36,45], ensuring the necessary flow of information in both directions.
Champions anchored at the clinic level played a pivotal role in the practical implementation and facilitation of the daily use of technology [31,33,35,37,38,43,48,51]. Additionally, these champions actively participated in meetings with senior management to discuss the technology and its implementation in the clinic.This position conferred potential influence over health personnel [33,35].Champions at the clinic level facilitated collaboration between employees, management, and suppliers [48].Fontaine et al. [36] identified respected champions at the clinical level, possessing authority and formal support from all leadership levels, as the most important factor for success.
Only one study reported that the champions received additional compensation for their role [36], while another study mentioned champions having dedicated time to fulfil their role [46].The remaining studies did not provide this information.

Recruiting for the role as champion
Several studies have reported different experiences regarding the management's selection of champions.A study highlighted the distinctions between a volunteered role and an appointed champion's role [31].Some studies underscored that appointed champions were chosen based on technological expertise and skills [41,48,51].Moreover, the selection criteria included champions' interest in the specific technology [42] or experiential skills [40].The remaining studies did not provide this information.
While the champion role was most frequently held by health personnel with clinical experience, one study deviated by hiring 150 newly qualified nurses as champions [30] for a large-scale implementation of an Electronic Health Record (EHR).Opting for clinical novices assisted in reducing implementation costs, as it avoided disrupting daily tasks and interfering with daily operations.According to Bullard [30], these super-user nurses became highly sought after post-implementation as a result of their technological confidence and competence.

Reported experiences of champions and health personnel
Drawing from the experiences of both champions and health personnel, it is essential for a champion to possess a combination of general knowledge and specific champion characteristics.Furthermore, champions are required to collaborate with individuals both within and outside the organization.The subsequent paragraphs delineate these experiences, categorizing them into four subsets: champions' contextual knowledge and expertise, preferred performance of the champion role, recognizing that a champion alone is insufficient, and distinguishing between reactive and proactive champions.

Champions' contextual knowledge and know-how
Health personnel with experience interacting with champions emphasized that a champion must be familiar with the department and its daily work routines [35,40].Knowledge of the department's daily routines made it easier for champions to facilitate the adaptation of technology.However, there was a divergence of opinions on whether champions were required to possess extensive clinical experience to fulfil their role.In most studies, having an experienced and competent clinician as a champion instilled a sense of confidence among health personnel.Conversely, Bullard's study [30] exhibited that health personnel were satisfied with newly qualified nurses in the role of champion, despite their initial skepticism.
It is a generally expected that champions should possess technological knowledge beyond that of other health professionals [37,41].Some health personnel perceived the champions as uncritical promoters of technology, with the impression that health personnel were being compelled to utilize technology [46].Champions could also overestimate the readiness of health personnel to implement a technology, especially during the early phases of the implementation process [32].Regardless of whether the champion is at the management level or the clinic level, champions themselves have acknowledged the importance of providing time and space for innovation.Moreover, the recruitment of champions should span all levels of the organization [34,46].Furthermore, champions must be familiar with daily work routines, work tools, and work surfaces [38,40,43].

Preferable performance of the champion role
The studies identified several preferable characteristics of successful champions.Health personnel favored champions utilizing positive words when discussing technology and exhibiting positive attitudes while facilitating and adapting it [33,34,37,38,41,46].Additionally, champions who were enthusiastic and engaging were considered good role models for the adoption of technology.Successful champions were perceived as knowledgeable and adept problem solvers who motivated and supported health personnel [41,43,44,48].They were also valued for being available and responding promptly when contacted [42].Health professionals noted that champions perceived as competent garnered respect in the organization [40].Moreover, some health personnel felt that some certain champions wielded a greater influence based on how they encouraged the use of the system [48].It was also emphasized that health personnel needed to feel it was safe to provide feedback to champions, especially when encountering difficulties or uncertainties [49].

A champion is not enough
The role of champions proved to be more demanding than expected [29,31,38], involving tasks such as handling an overwhelming number of questions or actively participating in the installation process to ensure the technology functions effectively in the department [29].Regardless of the organizational characteristics or the champion's profile, appointing the champion as a "solo implementation agent" is deemed unsuitable.If the organization begins with one champion, it is recommended that this individual promptly recruits others into the role [42].
Health personnel, reliant on champions' expertise, found it beneficial to have champions in all departments, and these champions had to be actively engaged in dayto-day operations [31,33,34,37].Champions themselves also noted that health personnel increased their technological expertise through their role as champions in the department [39].
Furthermore, the successful implementation of technology requires the collaboration of various professions and support functions, a task that cannot be solely addressed by a champion [29,43,48].In Orchard et.al. 's study [34], champions explicitly emphasized the necessity of support from other personnel in the organization, such as those responsible for the technical aspects and archiving routines, to provide essential assistance.
According to health personnel, the role of champions is vulnerable in case they become sick or leave their position [42,51].In some of the included studies, only one or a few hold the position of champion [37,38,42,48].Two studies observed that their implementations were not completed because champions left or reassigned for various reasons [32,51].The health professionals in the study by Owens and Charles [32] expressed that champions must be replaced in such cases.Further, the study of Olsen et al., 2021 [42] highlights the need for quicky building a champion network within the organization.
In a study presenting experiences from both health personnel and champions, Yuan et al. [31] found that personnel observed differences in the assistance provided by appointed and self-chosen champions.Appointed champions demonstrated the technology, answered questions from health personnel, but quickly lost patience and track of employees who had received training [31].Health personnel perceived that self-chosen champions were proactive and well-prepared to facilitate the utilization of technology, communicating with the staff as a group and being more competent in utilizing the technology in daily practice [31].Health personnel also noted that volunteer champions were supportive, positive, and proactive in promoting the technology, whereas appointed champions acted on request and had a more reactive approach [31].

Discussion
This review underscores the breadth of the concept of champion and the significant variation in the champion's role in implementation of technology in healthcare services.This finding supports the results from previous reviews [10,18,19,20].The majority of studies meeting our inclusion criteria did not specifically focus on the experiences of champions and health personnel regarding the champion role, with the exception of studies by Bullard [30], Gui et al. [29], Helmer-Smith et al. [33], Hogan-Murphy et al. [46], Rea et al. [50], and Yuan et al. [31].
The 23 studies encompassed in this review utilized 20 different terms for the champion role.In most studies, the champion's role was briefly described in terms of the duties it entailed or should entail.This may be linked to the fact that the role of champions was not the primary focus of the study, but rather one of the strategies in the implementation process being investigated.This result reinforces the conclusions drawn by Miech et al. [10] and Shea et al. [12] regarding the lack of united understandings of the concept.Furthermore, in Santos et al. 's [19] review, champions were only operationalized through presence or absence in 71.4% of the included studies.However, our review finds that there is a consistent and shared understanding that champions should promote and support technology implementation.
This suggests a general lack of information essential for understanding the pros, cons, and prerequisites for champions as a strategy within this field of knowledge.However, this review identifies, on a general basis, the types of support and structures required for champions to perform their role successfully from the perspectives of health personnel, contributing to Shea's conceptual model [12].
Regarding the organization of the role, this review identified champions holding both formal appointed and informal roles, working in management or clinical settings, being recruited for their clinical and/or technological expertise, and either volunteering or being hired with specific benefits for the role.Regardless of these variations, anchoring the role is crucial for both the individuals holding the champion role and the health personnel interacting with them.Anchoring, in this context, is associated with the clarity of the role's content and a match between role expectations and opportunities for fulfilment.Furthermore, the role should be valued by the management, preferably through dedicated time and/ or salary support [34,36,46].Additionally, our findings indicate that relying on a "solo champion" is vulnerable to issues such as illness, turnover, excessive workload, and individual champion performance [32,37].Based on these insights, it appears preferable to appoint multiple champions, with roles at both management and clinical levels [33].
Some studies have explored the selection of champions and its impact on role performance, revealing diverse experiences [30,31].Notably, Bullard [30], stands out for emphasizing long clinical experience, and hiring newly trained nurses as superusers to facilitate the use of electronic health records.Despite facing initial reluctance, these newly trained nurses gradually succeeded in their roles.This underscores the importance of considering contextual factors in the champion selection [30,52].In Bullard's study [30], the collaboration between newly trained nurses as digital natives and clinical experienced health personnel proved beneficial, highlighting the need to align champion selection with the organization's needs based on personal characteristics.This finding aligns with Melkas et al. 's [9] argument that implementing technology requires a deeper understanding of users, access to contextual know-how, and health personnel's tacit knowledge.
To meet role expectations and effectively leverage their professional and technological expertise, champions should embody personal qualities such as the ability to engage others, take a leadership role, be accessible, supportive, and communicate clearly.These qualities align with the key attributes for change in healthcare champions described by Bonawitz et al. [15].These attributes include influence, ownership, physical presence, persuasiveness, grit, and a participative leadership style (p.5).These findings suggest that the active performance of the role, beyond mere presence, is crucial for champions to be a successful strategy in technology implementation.Moreover, the recruitment process is not inconsequential.Identifying the right person for the role and providing them with adequate training, organizational support, and dedicated time to fulfill their responsibilities emerge as an important factor based on the insights from champions and health personnel.

Strengths and limitations
While this study benefits from identifying various terms associated with the role of champions, it acknowledges the possibility of missing some studies as a result of diverse descriptions of the role.Nonetheless, a notable strength of the study lies in its specific focus on the health personnel's experiences in holding the champion role and the broader experiences of health personnel concerning champions in technology implementation within healthcare services.This approach contributes valuable insights into the characteristics of experiences and attitudes toward the role of champions in implementing technology.Lastly, the study emphasizes the relationship between the experiences with the champion role and the organizational setting's characteristics.
The champion role was frequently inadequately defined [30, 33-37, 39, 41-47, 51], aligning with previous reviews [17,19,21].As indicated by van Laere and Aggestam [52], this lack of clarity complicates the identification and comparison of champions across studies.Studies that lacking a distinct definition of the champion's role were consequently excluded.Only studies written in English were included, introducing the possibility of overlooking relevant studies based on our chosen terms for identifying the champion's role.Most of the included studies focused on technology implementation in a general context, with champions being just one of several measures.This approach resulted in scant descriptions, as champions were often discussed in the results, discussion, or implications sections rather than being the central focus of the research.
As highlighted by Hall et al. [18]., methodological issues and inadequate reporting in studies of the champion role create challenges for conducting high-quality reviews, introducing uncertainty around the findings.We have adopted a similar approach to Santos et al. [19], including all studies even when some issues were identified during the quality assessment.Our review shares the same limitations as previous review by Santos et al. [19] on the champion role.

Practical implications, policy, and future research
The findings emphasize the significance of the relationship between experiences with the champion role and characteristics of organizational settings as crucial factors for success in the champion role.Clear anchoring of the role within the organization is vital and may impact routines, workflows, staffing, and budgets.Despite limited evidence on the experience of the champion's role, volunteering, hiring newly graduated health personnel, and appointing more than one champion are identified as facilitators of technology implementation.This study underscores the need for future empirical research including clear descriptions of the champion roles, details on study settings and the technologies to be adopted.This will enable the determination of outcomes and success factors in holding champions in technology implementation processes, transferability of knowledge between contexts and technologies as well as enhance the comparability of studies.Furthermore, there is a need for studies to explore experiences with the champion role, preferably from the perspective of multiple stakeholders, as well as focus on the champion role within various healthcare settings.

Conclusion
This study emphasizes that champions can hold significant positions when provided with a clear mandate, dedicated time, and training, contributing their professional, technological, and personal competencies to expedite technology adoption within services.It appears to be an advantage if the health personnel volunteer or apply for the role to facilitate engaged and proactive champions.The implementation of technology in healthcare services demands efforts from the entire service, and the experiences highlighted in this review exhibits that champions can play an important role.Consequently, empirical studies dedicated to the champion role, employing robust designs based current knowledge, are still needed to provide solid understanding of how champions can be a successful initiative when implementing technology in healthcare services.

Fig. 1
Fig. 1 Flow Chart illustrating the study selection and screening process

Table 1
Study characteristics